net/mlx5: fix restore info in non-tunnel traffic

net/mlx5: fix restore info in non-tunnel traffic

Tunnel offload API provides applications with ability to restore
packet outer headers after partial offload. Exact feature execution
depends on hardware abilities and PMD implementation. Hardware that is
supported by MLX5 PMD places a mark on a packet after partial offload.
PMD decodes that mark and provides application with required
information.
Application can call the restore API for packets that are part of
offloaded tunnel and not. It's up to a PMD to provide correct
information.
Current MLX5 tunnel offload implementation does not allow applications
to use flow MARK actions. It is restricted to tunnel offload use only.
This fault was triggered by application that did not activate tunnel
offload and called the restore API with a marked packet. The PMD tried
to decode the mark value and crashed. The patch decodes mark value
only if tunnel offload is active.

Fixes: 4ec6360de37d ("net/mlx5: implement tunnel offload")

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>